In the related art, an AD converter of a charge integration type that integrates a current by an integrator and executes AD conversion on an integral value is known. The AD converter is used for a radiation detector in which a signal is output as a current.
As the AD converter according to the related art, an AD converter in which an integrator is configured by an operational amplifier is suggested. In the AD converter, a current is input to an integration capacitor by a virtual ground of the operational amplifier and a charge according to the input current is accumulated in the integration capacitor. In addition, a voltage of the integration capacitor is output as an integral value.
Because the integrator according to the related art cannot integrate a current during resetting of the integration capacitor, integration precision is low. In addition, because the integrator includes the operational amplifier, power consumption is large.